ACTINIARIA 



195 



weak ectodermal, radial muscles. Actinopharynx with few (about 10) longitudinal ridges. Pairs of mesen- 

 teries arranged liexamerously (6 + 6 + 12) ; only 6 pairs perfect. Parietobasilar muscles like those of A . jan 

 mayeni. Typical nematocysts in the ectoderm of the column?, in the tentacles absent (? or if present very 

 sparse). Particular stinging capsules of the stinging battery very numerous 53 — 75 X 11 — 13 /i. Spirocysts 

 of the tentacles very numerous, from 22 X 2 /i to 55 X 3 (3,5) ^. Nematocysts with discernible basal part 

 to the spiral thread in the actinopharynx rather numerous, 26 — 34 X 5 //. 



Colour? 



Dimensions: Breadth of the pedal disc 2,4 resp. 2,7 cm, length of the column in contracted state 

 about 1,3 cm. 



Occurrence: 66°o8' N. i6°02' W. 729 fms. Bottom temp. — 

 0,8 (Ingolf-Exp. St. 125) 2 sp. 



Exterior aspect: The pedal disc is broad and does not seem 

 to form any cuticle. The form of the body is in contracted state rather 

 low and almost hemispheric. The surface of the body- wall is smooth; in 

 the distal part there were indistinct longitudinal furrows present. The 

 tentacles are short, the inner considerably broader and larger than the 

 outer, in number 48, probably liexamerously arranged (6+6-1-12 + 24), 

 the two first cycles are, however, very close. Because of the strong con- 

 traction of the specimens it was difficult to get a satisfactory diagram of 

 the arrangement of the tentacles. The form of the tentacles varies from 

 cylindrical to a little conical ; I have not observed any longitudinal fur- 

 rows on the tentacles, only indistinct transversal furrows, arisen by the contraction. The oral disc is very 

 wide and smooth, and in contracted state deeply excavated. The actinopharynx is short and, on account of 

 the contraction, transversally wrinkled, with aboral prolongations on the 12 perfect mesenteries, and pro- 

 vided with 10 longitudinal furrows between the insertions of the mesenteries. Two siphonoglyphes are 

 present. 



Anatomical description: The ectoderm of the column is thin and almost totally lost, so that 

 I cannot give any information of its structure. The mesogloea is thin or of ordinary thickness, in the region 

 of the sphincter, however, very thick. The sphincter is very strong and recalls that of A . jan mayeni. The 

 muscle meshes are small and now very closely packed, now more sparse; the sphincter shows, as far 

 as I can see, no tendency to stratification. The endodermal circular muscles are weak. The ectoderm of 

 the tentacles is high and probably contains no typical nematocysts, if really present they are ver>- sparse. 

 The outer tentacles are on the outside of the base provided with a stinging battery as in A. jan mayeni. The 

 nematocysts are, however, smaller here and variate in both specimens between 53 and 75 // in length and 

 II — 13 ^ in breadth. The spirocysts of the tentacles are extraordinarily numerous, between 22 X 2 to 55 X 

 3,5 [1 in size. The longitudinal muscles of the inner tentacles are much weaker on the outside of the base 

 than on the inside. The inner folds are namely much closer and often more than double as high as the outer 

 folds. They are often branched (textfig. 187 transverse section of inner tentacle). In contradistinction to 



25* 



Textfig. 187. .-inthosactis ingolfi. 

 Transverse section of inner tentacle. 



